/**
 * Clock.c -- Analog Clock Program
 *              (c) Charles Petzold, 1998
 */

#include <windows.h>
#include <math.h>

#define ID_TIMER 1
#define TWOPI (2*3.14159)

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("Clock");
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"), szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName,
                        TEXT("Analog Clock"),
                        WS_OVERLAPPEDWINDOW,
                        CW_USEDEFAULT,
                        CW_USEDEFAULT,
                        600,
                        600,
                        NULL,
                        NULL,
                        hInstance,
                        NULL);
    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}

void SetIsotropic(HDC hdc, int cxClient, int cyClient)
{
    SetMapMode(hdc, MM_ISOTROPIC);
    SetWindowExtEx(hdc, 1000, 1000, NULL);
    SetViewportExtEx(hdc, cxClient/2, -cyClient/2, NULL);
    SetViewportOrgEx(hdc, cxClient/2, cyClient/2, NULL);
}

void RotatePoint(POINT pt[], int iNum, int iAngle)
{
    int i;
    POINT ptTemp;
    for(i=0;i<iNum; i++) {
        ptTemp.x = (int)(pt[i].x*cos(TWOPI*iAngle/360)+pt[i].y*sin(TWOPI*iAngle/360));
        ptTemp.y = (int)(pt[i].y*cos(TWOPI*iAngle/360)+pt[i].x*cos(TWOPI*iAngle/360));
        pt[i] = ptTemp;
    }
}

void DrawClock(HDC hdc)
{
    int iAngle;
    POINT pt[3];
    for (iAngle=0; iAngle<360; iAngle+=6) {
        pt[0].x = 0;
        pt[0].y = 900;
        RotatePoint(pt, 1, iAngle);
        pt[2].x = pt[2].y = iAngle % 5 ? 33 : 100;
        pt[0].x -= pt[2].x / 2;
        pt[0].y -= pt[2].y / 2;
        pt[1].x = pt[0].x + pt[2].x;
        pt[1].y = pt[0].y + pt[2].y;
        SelectObject(hdc, GetStockObject(BLACK_BRUSH));
        Ellipse(hdc, pt[0].x, pt[0].y, pt[1].x, pt[1].y); 
    }
}

void DrawHands(HDC hdc, SYSTEMTIME *pst, BOOL fChange)
{
    static POINT pt[3][5] = {
        0, -150, 100, 0, 0, 600, -100, 0, 0, -150,
        0, -200, 50, 0, 0, 800, -50, 0, 0, -200,
        0, 0, 0, 0, 0, 0, 0, 0, 0,  800
    };
    int i, iAngle[3];
    POINT ptTemp[3][5];

    iAngle[0] = (pst->wHour * 30) % 360 + pst->wMinute / 2;
    iAngle[1] = pst->wMinute * 6;
    iAngle[2] = pst->wSecond * 6;

    memcpy(ptTemp, pt, sizeof(pt));
    for (i=fChange ? 0 : 2; i<3; i++) {
        RotatePoint(ptTemp[i], 5, iAngle[i]);
        Polyline(hdc, ptTemp[i], 5);
    }
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static int cxClient, cyClient;
    static SYSTEMTIME stPrevious;
    BOOL fChange;
    HDC hdc;
    PAINTSTRUCT ps;
    SYSTEMTIME st;

    switch (message)
    {
        case WM_CREATE: {
            SetTimer(hwnd, ID_TIMER, 1000, NULL);
            GetLocalTime(&st);
            stPrevious = st;
            return 0;
        }
        case WM_SIZE: {
            cxClient = LOWORD(lParam);
            cyClient = HIWORD(lParam);
            return 0;
        }        
        case WM_TIMER: {
            GetLocalTime(&st);
            fChange = st.wHour != stPrevious.wHour ||
                        st.wMinute != stPrevious.wMinute;
            hdc = GetDC(hwnd);
            SetIsotropic(hdc, cxClient, cyClient);
            SelectObject(hdc, GetStockObject(WHITE_PEN));
            DrawHands(hdc, &stPrevious, fChange);
            
            SelectObject(hdc, GetStockObject(BLACK_PEN));
            DrawHands(hdc, &st, TRUE);
            
            ReleaseDC(hwnd, hdc);

            stPrevious = st;
            return 0;
        }
        case WM_PAINT: {
            hdc = BeginPaint(hwnd, &ps);
            
            SetIsotropic(hdc, cxClient, cyClient);
            DrawClock(hdc);
            DrawHands(hdc, &stPrevious, TRUE);

            EndPaint(hwnd, &ps);
            return 0;
        }

        case WM_DESTROY: {
            KillTimer(hwnd, ID_TIMER);
            PostQuitMessage(0);
            return 0;
        }
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}